mesa/st: Fix vertex buffer leak
mesa/st: Fix vertex buffer leak

Make sure we unreference the vertex buffer pointers in a local array.
This fixes huge vertex buffer / memory leaks in mesa demos "fire" and "engine".

NOTE: This is a candidate for the 7.9 and 7.10 branches.

Signed-off-by: Thomas Hellstrom <a26490dfbee4be3d38287ad6448444504f58193c@vmware.com>

mapbox/glsl-optimizer,KTXSoftware/glsl2agal,benaadams/glsl-optimizer,djreep81/glsl-optimizer,KTXSoftware/glsl2agal,zz85/glsl-optimizer,zz85/glsl-optimizer,dellis1972/glsl-optimizer,tokyovigilante/glsl-optimizer,metora/MesaGLSLCompiler,bkaradzic/glsl-optimizer,zz85/glsl-optimizer,djreep81/glsl-optimizer,tokyovigilante/glsl-optimizer,zeux/glsl-optimizer,bkaradzic/glsl-optimizer,KTXSoftware/glsl2agal,metora/MesaGLSLCompiler,wolf96/glsl-optimizer,benaadams/glsl-optimizer,dellis1972/glsl-optimizer,zz85/glsl-optimizer,jbarczak/glsl-optimizer,djreep81/glsl-optimizer,jbarczak/glsl-optimizer,mcanthony/glsl-optimizer,metora/MesaGLSLCompiler,wolf96/glsl-optimizer,dellis1972/glsl-optimizer,jbarczak/glsl-optimizer,KTXSoftware/glsl2agal,zz85/glsl-optimizer,mapbox/glsl-optimizer,djreep81/glsl-optimizer,mcanthony/glsl-optimizer,wolf96/glsl-optimizer,mcanthony/glsl-optimizer,benaadams/glsl-optimizer,zeux/glsl-optimizer,bkaradzic/glsl-optimizer,adobe/glsl2agal,benaadams/glsl-optimizer,jbarczak/glsl-optimizer,bkaradzic/glsl-optimizer,adobe/glsl2agal,adobe/glsl2agal,zz85/glsl-optimizer,adobe/glsl2agal,mapbox/glsl-optimizer,mcanthony/glsl-optimizer,zeux/glsl-optimizer,mapbox/glsl-optimizer,KTXSoftware/glsl2agal,tokyovigilante/glsl-optimizer,mcanthony/glsl-optimizer,adobe/glsl2agal,zeux/glsl-optimizer,dellis1972/glsl-optimizer,zeux/glsl-optimizer,jbarczak/glsl-optimizer,dellis1972/glsl-optimizer,benaadams/glsl-optimizer,tokyovigilante/glsl-optimizer,wolf96/glsl-optimizer,djreep81/glsl-optimizer,bkaradzic/glsl-optimizer,wolf96/glsl-optimizer,tokyovigilante/glsl-optimizer,mapbox/glsl-optimizer,benaadams/glsl-optimizer